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(http://www.renewableenergyworld.com/rea/tech/geothermal-energy) This is a very clean, environmentally friendly and sustainable energy source. It is the heat from the earth crust. The heart of the earth is about 12000 degrees farenheit. Geothermal systems tap into this inexhaustive though not generally available energy source. Example is Reykjavik the capital of Iceland which islocated near hot springs.

Decayed radioactive subatsnces trapped in the earth crust heats it up and the heat is carried by water and magma to the earth surface which heats springs up. The pressurized steam from superheated water beneath the earth surface is used to generate electricity. It does not require complex and vast structures like in the fossil fuel extraction.

Natural geothermal vents are not widely available. So, artificial vents are driiled to the ground to reach the hot rocks below, and wateris injected into it to produce steam.

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Geothermal energy is not as clean as it looks and sould not even be considered as renewable, as many people believe.

In each geothermal energy system there is at least one source of heat (a magmatic chamber for instance), which transfers heat to the fluid. Every time the water enters the reservoir, it slowly cools the magmatic chamber, or the plutonites that act as heat source and in case these heat sources are not big enough, or re-heated by a mechanism, the geothermal energy system is to be depleted.

Sulfur, salt and heavy metals, most of the times in large concentrations exist in geothermal fluids, because their quality is affected by the earth and rocks of the reservoir (magmatic origin). Geothermal fluids are not environmental freindly neither healthy for humans, and in certain occasions- depending on the reservoir are extremely dangerous.

In Greece, (1990's), a geothermal energy installation in Nisyros island was destroyed after only 5 years of function. The engineers that did the study, did not measure certain concentrations right, and due to corrosion and other causes (H2S), the geothermal station closed.

To conclude, geothermal fluids are not to be considered as clean and geothermal energy is not an easy energy source to be harnessed. Also it is not renewable, but it can be sustainable, under certain circumstances.

I underrstand from point of view of arguement however i belive that geothermal is still viable and safe if right technology and safety regulations are been observed to details because the dependency on fossil fuels need to be reduced.

The issue of compliance to best practices is the main task as well as strict monitoring.

A comprehensive fluid studies, reservoir chararacterization against potential hazards can readily be put in pllace before the design and installation alongside choice of structural materials.

It is very important, for someone to understand that geothermal energy is a rare source of energy. Particularly in Europe, only 3 countries have the ability to produce energy from geothermal reservoirs, Greece, Italy and Iceland.

This cannot of course be done everywhere in these countries. Hot spots need to be located (hign enthalpy). and i write this in order to clarify that producing electricity from a geothermal field is something completely different than heat pumps (low enthalpy), that can be used for the production of hot water, or to make a place warmer. Heat pumps can be installed in other countries too (geological grade). England, and the UK generally is not a country that could be greatly benefited by geothermal energy.

Geothermal energy is closely connected to volcanic activity, or older volcanic arches, where active magmatic chambers can still be found relatively close to the surface. Volcanic activity, is closely connected to seismic activity, which is something that cannot guarantee safety for geothermal installations and humans involved by many aspects.

To summarize, geothermal energy is not as safe as someone may believe, and its major disadvantage as Michael Saiki pointed is that it is something rare indeed.

I would like to say that I agree with Menelaos
above that geothermal energy is not as safe as everyone believes.

In 2006, a major geothermal project held in a
town called Basel in Switzerland, was put on hold because it caused a 3.4
magnitude earthquake followed by thousands of aftershocks causing damages in the
whole town.

In 2009, another major geothermal project held in
California, in The Geysers, the world’s largest dry-stream
geothermal steam field, was abandoned after the workers faced difficulties
concerning the drilling.

Nowadays, industries try to limit the risk in
order to continue extracting energy from the earth. The VP of legislative and
regulatory affairs atMidAmerican EnergyHoldings Company, Mr. Jonathan Weisgall, said: "We need to de-risk this industry. The tech
costs have to come down for investors too, and all the time there is the
spectre of low natural gas prices. But above all we need regulatory certainty."

To sum up, geothermal energy is said to have
great potential; however it needs further research in order to be safe enough
to use it more in the future.

Geothermal energy might be clean and renewable but is not
safe. It leads to earthquakes and some projects had to shut down because of these
consequences. The drilling procedure requires to drill deep enough in order to
reach the hot rocks that can turn the injected water into steam, and this can
result to unwanted and unpredicted earthquakes. Some villages that where
located near geothermal facilities experienced the earthquakes and continued to
experienced them for some time even after those facilities where shut down. The earthquakes are not so powerful to cause
deaths but are strong enough to cause problems to a property. There are fears
that the deeper the drilling is in the areas that have geothermal potentials, the
more are the chances to cause an earthquake.

Dear Xenios,
The technology which you are referring to is the Enhanced/Engineered geothermal systems which are working on the same principle as shale gas hydrofracking.
Because rocks hold the most part of heat and not water the idea is to open up the fractures to create an underground reservoir for the water to circulate. Drilling in these depths of up to 7km can cause seismic events like in Basel, Switzerland where the drilling was cancelled due to earthquakes that hopefully only caused material damage.
Although most seismic events are not likely to cause any material damage there is a lot of research on this area. THere are some non condesed gases thought associated with the procedure.

I believe that until the reasons at pilot units are fully understood, large scale commercial applications of this technology should not be applied. There is a lot of research going in this area with many countries cooperationg together and this shows the potential this sector has to offer.

I would like to disagree with micheal saiki on the issue of geothermal advantages. on the issue of pollution it is been analysed that geothermal fluids contain dissolved gasses which are released to the atmosphere, this toxic gases are carbon dioxide which I guess most of us know the consequence, and hydrogen sulphide. All this gases are denser than air hence they can collect in in pits and depressions or confined spaces.
Geothermal energy is exhaustible because the well can run out and once the geothermal well has run it cannot be reignited because the magma temperatures have dropped and also another concern is that the process of reinjection compared to the profits is marginal hence it makes it difficult. The only option is to drill new wells which are costly.
The other disadvantage of geothermal energy is that once geothermal fluids have been extracted it reduces the pressure in the underground reservoirs and this resulted in the land sinking. The largest subsidence in record is at Weireke. In 2005 the ground was 14M loser than it was before the power plant was constructed and also the land moves sideways as it sinks.
Sourcehttp://www.teara.govt.nz/en/geothermal-energy/5

While everyone disagrees with Micheal, I tend to see reason with his opinion. We can all critically churn out disadvantages and risks associated with ALL forms of energy(including fossil fuels) off the top of our heads, thats relatively easy. But looking at the bigger picture, our race is fast running out of fossil fuel reserves! Man in his problem solving nature is continuously devising means of optimally extracting other forms of energy to cushion the effect of limited fossil fuel reserves. Geothermal energy generation is one of them. While the risk of earthquakes emerging as a result of extraction of geothermal energy exists as its largest drawback, its advantages are are numerous. Theoretically the reserves are inexhaustible. It is a sustainable cycle as the carrier medium(water) can be easily injected back to the earth through injection wells. Studies have shown that it is a far cheaper option than fossil fuel energy as the capital investment for the end user is purchase of the heat pumps required and when this is considered over time, it evens out and becomes a cheaper source of energy generaion. In conclusion, I think it is the future of energy generation for our planet.

I admit that you have a point. The energy needs are increasing whereas fossil fuels are decreasing rapidly. This means that humanity sould try in its entirety to find alternative sources of energy, that are sustainable, without excluding geothermy.

But geothermal energy compared to other sustainable forms of energy has many more disadvantages. By the aspect of safety is not as safe as others, as explained by previous posts. Geothermal fluids are dangerous too, for humans and the environment. Sometimes beyond H2S, they contain large concetrations of heavy metals and dangerous substances, such as barium, vanadium, arsenic, and others. Check my previous posts please.

In this post i would like to provide some information about costs. Geothermal stations are very expensive compared to renewable resources installations, or fossil fuel exploitation costs. The tiny geothermal station, that was built on Nisyros (Greek island) costed for the Greek state 5 billions of drachmas, which is translated to about 11.8 millions english pounds. The station stopped working after only 5 years, due to problems caused by certain concentrations of the geothermal fluids (mostly salts that were formed inside the pipes and this the reasons why the installations stopped producing).

Please consider how many things could be bought with these money, that would cover the energy needs of the island (wind turbines, solar panels, or even fossil fuels). I am not an expert in geothermy , but geothermal power stations must have big preservation costs (e.g change pipes due to corrosion), which sould be added in the disadvantages list. Other form of energy will not have such costs, especially in a Greek island where the weather is good.

To some extent, geothermal is a clean, safe and
environmentally friendly source of energy especially if compared with energy
from fossil fuels because it does not involve combustion of fuel however Steam fromGeothermal wells contains
non-condensable gases such as carbon dioxide (90% of the steam),Hydrogen
Sulphide and smaller amounts of Ammonia, Methane, Nitrogen, Hydrogen and Mercury,
Boron [Harsh and Sukanta
et al..2007] whichcontribute to air pollution (greenhouse emissions) though the quantity of
greenhouse gases produced per unit weight of steam produced is far much less
compared to that from the combustion of fossil fuels. Geothermal energy may
also cause chemical pollution of the environment. Mercury and Ammonia produced
from geothermal wells can also result in contamination of the soil and
vegetation through leaching. Waste water from geothermal reservoirs containing
such chemicals may mix with ground water for the case of shallow aquifers
causing contamination [Harsh and Sukanta et al..2007]. Noise
pollution can also occur during the drilling of geothermal wells however this
can be contained if appropriate silencers are used.

The good news is that the current technologies can
allow the carbon dioxide and other gases produced from geothermal wells to
remain in liquid form and then re-injected back into the reservoirs without
passing into the atmosphere thus causing no environmental pollution and a good
example is for the case of binary geothermal plants.

The withdrawal of Geothermal fluids from the
reservoir fora long time at a rate
higher than the recharge by surface watermay lead to lowering of the ground water table, land subsidence and
trigger seismicity [ Harsh and Sukanta et al..2007] however these
effects can still be overcome by re-injection ofwaste water after extraction of energy.Prolonged
geothermal exploitation, subsidence and re-injection could however trigger
earthquakes in critically stressed areas. According to experimental studies carried out
on the Rangely oil field-Colorado , HarshandSukanta et al..2007cites Raleigh et al.,
1972saying that injection of fluid can change subsurface pore fluid pressure
and thereby trigger earthquakes

In conclusion, pollution effects caused by geothermal
power can be controlled through re-injection of waste water fluids as already
discussed and thus leading to almost zero greenhouse gas emissions and zero
chemical pollution making geothermal a clean alternative source of energy for
the future however, further research and development needs to be done especially on the issue of
re-injection having the possibility of triggering earthquakes. Enhanced Geothermal Systems need to be developed .Thorough
scientific studies need to be carried
out to determine the geologic and tectonic conditions existing at the site prior
to well drilling [Ronald,2008]. There is also need for continuous inspections
of geothermal sitesfor any natural or
induced seismic events. It is also important to construct geothermal plants in
remote areas to reduce on the severeeffects
of unexpected calamities like earth quakes.
Sensitization/training programs of the residents in the neighbourhood are also crucial
to inform the residents of the possible safety measures in case of any signs of
seismic events. Workers on geothermal plants need to be protected with
protective gear to avoid the effects of fumes from geothermal reservoirs and
also there is need to enforce legislation/regulations in order to minimize the safety and environmental risks
associated with geothermal power plants.

The world is slowly going towards green
technology, since environmental pollution becomes a significant concern over
the years. As the other students revealed, geothermal energy is a clean,
renewable energy and can replace existing energy generated from fossil fuels.
This was illustrated in 2007 by the Energy Department, since it suggested that
geothermal theory could produce 60,000 times a nation’s annual energy
usage.I agree with Michael Saiki,
saying that geothermal energy has many advantages, since the main disadvantage
producing geothermal energy is that drilling may produce earthquakes. Producing
geothermal energy must continue to develop since its advantages outweigh the
disadvantages. To conclude geothermal energy is called a renewable energy
because the water is replenished by rainfall, and the heat is continuously
produced by the Earth.

Dear Frixos, i agree with many of the things you have written, such as that ''the world is slowly going towards green technology'' as well as with your position that geothermal energy is a kind of renewable energy. Magmatic chamber are partially reheated and the geothermal reservoir water is somehow renewed because of rain, so you are right, in this point.

However, i have to disagree partially to one of the things that you refer, that geothermal energy can produce 60000 times a nation's annual energy, because the number seems too big to me.

People do not only need hot water and electricity, that can be produced by geothermal fluids under certain circumstances, but also liquid fuels, for cars and engines, so even in Iceland people cannot completely depend on geothermy. To conclude, covering completely a nation's energy by geothermy is an outopia, and even in Iceland people cannot completely depend on geothermy to cover their neeeds.

I agree with you that further developments in all renewable energy systems are welcomed, so development of all kinds in producing geothermal energy must continue.

The contribution of geothermal energy as a form of renewable energy for meeting the rising energy demand is of importance to several regions despite the fact that some of my colleagues have pointed out some shortfalls which all forms of energy has its own pitfalls, afterall, there is no benefit without its correlative burden.

Geothermal energy could be said to be clean as a pure aspect of its source of heat that emanates naturally from the earthcrust. The crust makes up only 0.4% of the total mass of the planet, the remaining 99.6% being hotter than 500°C within the crust, increasing to 5000°C at the core. The pressures are constantly generating the heat naturally. This means that geothermal energy is infinite in its nature, as it is naturally renewable. Safety is a function of the technology being used and the level of safety and risk awareness of the operating organisations. Also, any system is said to be safe if all its known risks are suppressed in a controllable manner and Geothermal energy has not led to any major accidents in regions where it's been used.

Its Environmental implication has been the major contention for my colleagues especially the associated earthquake and polluted concentrates in the process. Earthquakes are natural disasters and there hasn't be any proof to draw the distinct line that geothermal energy system had led to this phenomenal occurence. The geothermal wells are drilled to an average depth of 6km to harness the heat required compared to the radius of the earth which is about 6000km (regions where the earthcrust is thin such as Iceland and Northsea on the Continental Shelf require less drilling depth). Also for the pollutants involved, new viable technologies are in place to optimise (example is the system, which is called GEESOR (Geothermal Energy Extraction System Organic Rankine), overcomes the problems of re-injection, two-phase fluid movement and environmental pollution by using a clean working fluid in a closed cycle).

Lastly, sustainability could be attained more in regions where the earthcrust is thin and geothermal activities occur naturally. Like in the Iceland where this energy has been harnessed to heat-up their buildings and used for the steam turbines. Other regions in the world are still being studied for future usuage.

The enemity between energy supply and the environment has always been the a key issue and also limited the use of recent technology to harness these sources of energy. Significant environmental impacts include conflicts in land use, air pollution, subsidence[1] Water pollution, induced seismicity, blowouts, and noise, and every country has encountered some difficulty with one or more of these problems.

Cleanliness: The quantity of emission released by geothermal energy as compared to fossil fuel sources makes it the cleanest form of energy. Gases such as carbon dioxide and nitrogen dioxide which are common with fossil fuel emissions. “Geothermal fields produce only about one-sixth of the carbon dioxide that a relatively clean natural-gas-fueled power plant produces, and very little if any, of the nitrogen dioxide or sulfur-bearing gases. Binary plants, which are closed cycle operations, release essentially no emissions”. (U.S. Department of Energry)[2]

Availability: Geothermal energy is available all year round, irresptive of weather, and no mining required when compared to coal mining and extraction.

Renewability and Environmental Impact: The amount of energy taken out can be re-injected back to the earth, making it a sustainable and renewable energy source. Geothermal plants releases minimal steam, gases, dissolved salt.

All of these features makes geothermal energy a more reliable, economical and cost effect when compared to other energy sources.

Due to growing concerns about the environmental effects of
using some energy generation techniques, there has been a constant quest to
develop new and enhance older techniques which have little or no effects on the
environment. Geothermal simple means using the natural energy of the earth,
believe it or not geothermal energy has been in use since the Stone Age. Back
then it was just used for hot springs and heating of buildings. The use of
geothermal energy for power generation did not come into play till the 20th
century. Geothermal energy is obtained as heat energy as it is been released
from the earth core or when neighbouring rocks around the earth core are melted
and migrate to the surface of the earth as hot molten magma.

Geothermal energy has been classified as a renewable energy
source but some amount of green house gases are released (1-3% of the amount of
CO2 and SO2 gases of that of coal combustion).Although
these values are relatively small compared to other non-renewable energy
sources there have been several debates about the environmental impacts. Other
undesired impurities associated with geothermal energy include radioactive
elements like mercury, antimony etc. Aside these elements and gases there have
been no other environmental concerns.

I would like to end this piece by saying, considering these
factors the economics, availability and environmental impacts of this energy
source it would be wise if the energy sector increases its dependence on
geothermal energy. It’s a step closer to achieving the total or temporary
reduction of emitted green house gases.

Geothermal energy is another form of renewable energy that
if adequately harness would help to reduce the impact of global climate change
because its pollution free, cheap, reliable and abundant. At the moment there
are about 98 operating plant of geothermal with an installed capacity of about
10,959.7 all over the world. Geothermal energy is the energy that is formed and
stored from the planet earth about 20% from the earth crust and 80% from the
mineral decay, a shallow depth of about 10meters will provide a temperature of
about 10-16
ͦC thermal gradient. Due to the temperature difference between the earth crust
and the surface there is a steady supply of heat that can be converted
to generate electricity.

With massive investment in the R & D in to this
technology, it has a lot of potential to supply electricity especially for
heating and with less greenhouse emission per unit of energy produce as compare
to other conventional source of energy such as fossils fuels in an environmentally
friendly manner.

In response to some issues raised on this post, I will like to chip in some thoughts

To start with, I will like to acknowledge that there is not any source of energy that will not have its drawbacks. What is important however, is how better it weighs compared to existing methods. Geothermal energy has its own, no doubt. There will always be teething problems and there will be permanent ones as well. Almost all projects have negative environmental impacts.

Part of the enviromental effects of geothermal energy is heat pollution. I quote from DiPippo (1991a) as cited in [1] "Considering only thermal discharges at the plant site, a geothermal plant is two to three times worse than a nuclear power plant with respect to thermal pollution, and the size of the waste heat rejection system for a 100 MW geothermal plant will be about the same as for a 500 MW gas turbine combined cycle"

Other potential areas of concern in the use of geothermal energy are the disturbance of natural hyrothermal manifestations such as geysers, hotspring and mudpots. Land subsidence is al so a major issue. This occurs when the geothermal fluid production rates are much greater that the recharge rates. The formation will manifest itself in as a lowering of the surface elevation, leading to surface subsidence [1]

Like I pointed out earlier though, some problems will manifest before the solutions are found out. This is what I think geothermal energy is going through. Its future looks good from my own perspective

Geothermal energy systems typically work by drilling boreholes to access hot bedrocks that are often buried deep underground. Water is then pumped into the boreholes where it creates steam that can be used to drive turbines and produce power.
Advocates of the technology argue that it could provide huge amounts of reliable zero carbon power.
However, there have been concerns that the drilling of deep boreholes can result in an increased risk of small earthquakes which, while unlikely to be large enough to cause serious damage, could affect buildings' foundations.
The new US safeguards look set to be introduced after a project run by Altarock Energy in California was reportedly shut down because of concerns over the impact of drilling.
Altarock has denied allegations from local residents that it underplayed the earthquake risks associated with the project, and refused to comment publicly on whether its drilling operation at the site is still going ahead."

Geothermal energy is clean, renewable energy from heat simmering within the earth's bedrock.

Geothermal's potential as a clean energy source has raised huge hopes, and its advocates believe it could put a significant dent in American dependence on fossil fuels.

The earth's heat is always there waiting to be tapped, unlike wind and solar power, which are intermittent and thus more fickle. According to a 2007 geothermal report financed by the Energy Department, advanced geothermal power could in theory produce as much as 60,000 times the nation's annual energy usage. President Obama has cited geothermal power as part of the "clean energy transformation" that a climate bill now before Congress could bring about.

Power companies have long produced limited amounts of geothermal energy by tapping shallow steam beds, often beneath geysers or vents called fumaroles. Those projects can induce earthquakes, although most are small. But for geothermal energy to be used more widely, engineers need to find a way to draw on the heat at deeper levels percolating in the earth's core.

But because large earthquakes tend to originate at great depths, breaking rock that far down carries more serious risk, seismologists say. Seismologists have long known that human activities can trigger quakes, but they say the science is not developed enough to say for certain what will or will not set off a major temblor.

The technique to tap geothermal energy creates earthquakes because it requires injecting water at great pressure down drilled holes to fracture the deep bedrock. The opening of each fracture is, literally, a tiny earthquake in which subterranean stresses rip apart a weak vein, crack or fault in the rock. The high-pressure water can be thought of loosely as a lubricant that makes it easier for those forces to slide the earth along the weak points, creating a web or network of fractures.

On Dec. 8, 2006, Markus O. Häring's geothermal project in Basel, Switzerland, was suspended when it set off an earthquake, shaking and damaging buildings and terrifying many.

The project was shut down permanently on Dec. 10, 2009, after a government study determined that earthquakes generated by the project were likely to do millions of dollars in damage each year.

In late June 2009, an American start-up company, AltaRock Energy, was set to begin using nearly the same method to drill deep into ground laced with fault lines in an area two hours' drive north of San Francisco.

Residents of the region, which straddles Lake and Sonoma Counties, have already been protesting swarms of smaller earthquakes set off by a less geologically invasive set of energy projects there. AltaRock officials said that they chose the spot in part because the history of mostly small quakes reassured them that the risks were limited.

Like the effort in Basel, the new project will tap geothermal energy by fracturing hard rock more than two miles deep to extract its heat. AltaRock, founded by Susan Petty, a veteran geothermal researcher, has secured more than $36 million from the Energy Department and several large venture-capital firms, including Kleiner Perkins Caufield & Byers, and Google.

The California project is the first of dozens that could be operating in the United States in the next several years, driven by a push to cut emissions of heat-trapping gases and the Obama administration's support for renewable energy.

Altough i believe geothermal energy to be a safe and renewable energy, i found it interesting some colleagues studying oil and Gas, that defend shale gas on some posts and are afraid of steam energy. There are two main types of geothermal, one you inject the water into hot rocks (similar ideas to fracking) and the other you use the natural water as long as it is used in a reasonbly manner it should be safe.

One of the dangers of this energy which i faced in the past, is the existance of radioactive rocks near the geothermal active zone, this should not be overlooked, as it can cause harm both to workers as users of this type of energy. This might contaminate the water or the waste generated by the system as some colleagues have stated.

Nevertheless in the usage of geothermal fluid for climatization this problem becomes even biger and bigger as the heated fluid will contact directly to the air people will bread.

Geothermal energy uses the heat energy of the
Earth to produce heat or electrical power for humanity’s use. Geothermal works
as an alternative energy source because the inside of the Earth is much hotter
than the surface. My position is that geothermal energy is a renewable energy
source which is clean as it does not pollute, and is also very well suited for
home heating and cooling.In
Geothermal energy, the heat is extracted directly unlike crude oil that you
need to burn it. Burning reduces the amount of heat capable of being obtained
if effected directly . Hence, the efficiency of the process is reduced.Also the volume of
water is almost constant as it is recycled back to the ground, heated up and
reused, but the crude oil is not recyclable in this regard.

Geothermal heat pumps for
ground source heating do have higher capital costs but is offset by their lower
operational costs compared to other forms of domestic heating and cooling
(HVAC) systems. Generally speaking, the lifespan of a geothermal heat pump installation is much longer than for a
conventional heating and cooling system, but their overall economic benefit and
payback period will depend primarily on usage and the relative costs of utility
supplied electricity and fuels used for heating and cooling the home, thus
supporting the view that Geothermal energy is a clean, safe, environmentally
comforting and massively sustainable energy resource.

As my classmates mentioned before, geothermal is a promising energy and has pros and cons. I believe that every coin has two sides. When we are considering whether to encourage or spur this energy application or not, it is suggested to balance its advantages and weaknesses firstly. In my opinion, the drawbacks of thermal energy outweighs its advantages. And most important thing is that there still are many uncertainties existed in this energy.

The biggest problem for this energy is that it can result in earthquake during operation. This has already posted by my classmates. Secondly, thetemperatureand pressure of geothermal steam are nothigh as traditional thermal power, leading lower utilization. Theefficiency of oldgenerator setlikeGaysers is only 14.3%, so that the coolingwaterused is morethantheordinarypower plant,and the thermal pollutionis also more serious. Furthermore, the resources of geothermal energy are not uniformly distributedin the world and its renewable period is long.

To sum up, there are some uncertainties of geothermal energy, and it is hard to be widespread applied in short term.

I totally agree with you Siwei. The cons for Geothermal steam generation to create electricity far outweigh the pros. The issues with pollution, earthquakes and corrosion just bring too many problems. Additionally, as the other posts have mentioned you have to be in the right place on the planet to make the most of it!!
However, all is not lost! As mentioned by Igwe in her post there is a growing trend for small scale geothermal energy in the home, that being the Ground Source Heat Pump (GSHP). These are not really practical in urban areas but if you live in the country and have enough land then I believe this is the way ahead (I know my neighbour has one!).
A certain amount of electricity is needed to run the pumps, which if sourced from solar panels or wind can make the system completely renewable. Equally, if the system is designed and installed correctly the Coefficient of Performance is about 3.2, i.e. the energy gained compared to that used is substantial enough to make a real difference. When you multiply this type of geothermal energy across 1000's of households and businesses that use it the true benefit can be seen. On average a GSHP can reduce the need for fossil fuel heating from between 50%-100% depending on the installation. The take up of this source of energy has been fairly low to date, since 2008 the demand has increased 12 fold but it is still only one third of the energy produced by solar heating, but with increasing economies of scale it is becoming more affordable.
Mark

Like every other source of energy, geothermal has its bad sides. In the case of the fluids drawn from the deep
earth, which carry a mixture of gases such as carbon dioxide, hydrogen sulfide,
methane and ammonia, these gases can be arrested. CO2 can be captured for
storage and used in food & beverage applications, hydrogen sulfide can be
disposed by conversion to sulfate ions in an aqueous solution, ammonia gas is
used in the fertilizer industry and methane can be used to create many
different compounds and products. There do already exist technologies that can
tackle these effects. The effect we should concern ourselves most is the issue
of subsidence. Extraction of geothermal fluids reduces the pressure in
underground reservoirs and can cause the land to sink. Example is in the case
of this effect at Wairakei, where the centre of the subsidence bowl is sinking
at a rate of about half a meter every year.

Geothermal power requires no fuel at start point and generates electricity it is a great benefit Earth crust temperature will rise when we go deeper typically 30-50 meters down temperature will rises one degree Celsius, it is also depend on the rock types and locationif we can found good geothermal gradient having stable rock properties according to geothermal activity according to survey it need initial capital cost to drill to the rock and start geothermal power that plant can power entire cities, since this kind of energy don’t emit greenhouse gases means no impact on environment smaller power plants can supply rural villages or to individual homes while in large area which shows it’s great advantage but it has some problems associated with this plant like we can’t build this kind of plant to any location and only choose particular place having hot rocks of a suitable type, at a depth these two parameter are consider and the steam which generated through a site may be longer time which is risky for the people who lives around and also a chance of hazardous gases or minerals like Arsenic, mercury, lithium and boron May comes out and disposal of these is difficultFaiza khatri M.Sc oil and gas engineering

I am writing just to let some classmates know that there are some applications in geothermal energy exploitation, which are considered very friendly to the environment.

It is truth that some conventional methods release emissions to the atmosphere, but in comparison with other energy producing techniques these are negligible. Local depletion is possible and should be avoided with proper management. Also, the geothermal potential is everywhere around the planet the only issue is how deep should we penetrate in order to produce economically viable electricity. Discussing about geothermal energy we should not forget that this source is available 24 hours per day and 365 days per year.

I disagree with statement that Menelaos made saying that electricity cannot cover completely our demands for instance the demand of transportation. I would like to mention that we can produce geothermal electricity in order not producing it by using fossil fuels in combustion plants, and hence, extending their life for transportation usage. Moreover, in case of having plenty of energy in one form, while having lack of another we could easily apply it for instance, to produce liquid fuels from coal or to produce hydrogen by electrolyzing the water. Also, electric vehicles have been introduced many years before but it is obvious that global oil and gas companies are not interested in this independence of main consumer which is the sector of transportation.

To get to the main point I will present two unconventional methods. The first is the down-hole closed-loop heat exchanger which is actually at the developing stage. The first method is based on binary cycle power production utilizing a single well. The heat exchanger is located down-hole and the first working fluid is circulated from the surface to the bottom where heat of the rock is transferred through the heat exchanger. When heated fluid returns to the surface it transfers the heat to the secondary fluid which actually will drive the turbine and subsequently the generator will be enabled to produce electricity. The two working fluids are isolated in different loops thus avoiding the potential impurities of the formation been released.

The second method known as dual pipe heat exchanger is industrially available. In this technique working fluid is injected from the annular space down-hole where the bottom is isolated and when heat is transferred to the fluid is extracted from the inner pipe. Then the vapor will provide the turbine's rotation and therefore the generator's shaft rotation. Electricity load will be produced in a clean and effective way. The only possible emission to the atmosphere is water vapor.

Both methods are using single well which is significant point when speaking about high drilling costs.

Dear Sergio, i like to see good friends like you making interesting posts, contributing information to our discussion topic.

I want to mention 2 basic commonly accepted energy approaches. At first heat is the worst form of energy for the reason it cannot be easily converted to other forms, such as kinetic for instance, without tremendous energy losses. On the other hand, other forms of energy, such as chemical can be easily converted to others (kinetic, thermal and others). This means that we can turn heat to other energy forms, we just do not prefer it because of the amount of energy we lose.

Producing electricity from high enthalpy (H) sources is a completely different thing. In Europe only 3 countries can do this as referred in previous posts Iceland, Italy and Greece.

Regarding to the cars you are right. Hydrogen could be used under certain circumstances instead of oil. But how about a plane, or the energy cost of launcing a missle? Liquid hydrocarbons such as oil release great amounts of energy when burnt and at least for now are the only fossil fuels to be used in order to put a satellite in orbit for instance. This is what i was meaning when i wrote, that we cannot completely depend on geothermal energy only, because it cannot completely cover our needs. For sure, the usage of other forms of energy, (such as geothermal) can extend the life of fossil fuels as you have written in the post above.

In this case, I would like you to explain something, if heat is the worst energy form, why transportation is still based on internal combustion engines, which firstly produce heat from the fuel and then it is converted to kinetic energy. Also, why you believe we should continue using such inefficient engines, where heat is unable to be converted adequately and we are wasting such important resources? Moreover, just to inform you that the yield of these engines commonly varies between 20-30%. Obviously, you know that this technology exists more than 120 years and its development through these years cannot exceed the 30% of energy utilization. Have you ever asked yourself why this could be happening? In my opinion this is because of high oil and gas exploration and exploitation costs which have to be recovered and high consumption is one way. The conclusion is that we should stop using hydrocarbons in an inefficient way.

Hydrocarbons are the main source for three sectors, these are; transportation, electricity generation and chemical utilization. I did not note in this blog someone claiming that we are planning to rely completely on geothermal energy source. But it is shame burning gas or heavier hydrocarbons to produce electricity. Also, I will agree that you are not professional in geothermal energy, but you should be a professional in geosciences so you could mention that the Earth's heat is everywhere. The only issues acting as barrier to the exploitation of this energy source is the high costs of drilling and of the equipment required for electricity generation, but we are not sure if it is not someone's effort to keep this energy source unpopular. I hope you are getting the point. I think when this limit will be outreached, there will be another issue affecting negatively geothermal exploitation. We are made to be addicted to hydrocarbons, although in my opinion we should distribute their utilization better and do it right now, in order to meet the demands of the future.

In my first post in this topic, I presented a couple of techniques that are not dangerous minimizing the corrosion. Also, hazards related to formation contaminants are also avoided. Maybe we are not able to send a rocket to the space by using geothermal energy, but such activities, which are very rare, are worth burning hydrocarbons. In contrast with taking the car and going for a cup of coffee and then by the time reaching the city center spending 15 minutes looking for parking and wasting petrol, which was created millions of years before thank to rare combination of specific conditions.

I think that you forgot that we have to reduce CO2 and CH4 emissions. Thus in the next future probably we are going to use electric means of transportation, as hydrogen utilization requires high quality technology. But when we are discussing about electric cars the source of their energy will not be a hydrocarbon combustion plant as you would like according to your excitement of the great energy released when burning oil and gas.

The fact that geothermal energy is potentially everywhere and there are a lot of abandoned wells mean that we have a very good solution for meeting the increased demands. Finally, I am going to remind you that the geothermal energy is the only renewable source available 24 hours per day, all the year around. The coefficient of this energy conversion is around 80%, while other renewable sources appear to have this factor significantly lower. The supply stability provided by this renewable energy can be used for unconventional fuel production like CTL or GTL in case when electricity is less important than fuels. Finally, I would like to hear any comments about the way I am thinking.

As our reliance on fossil fuels have
started to increase, geothermal energy is seen as the new source of power
generation by digging out the heat stored inside the earth. Though not used
fully due to factors such as location and high costs but in the years to come
when fossil fuels would start to diminish, it will turn out to be the cheapest
source of power generation. Geothermal energy suffers from its own advantages
and disadvantages as described below.

Advantages of Geothermal Energy:

1.Significant Cost Saving : Geothermal energy generally involves low running costs since it saves
80% costs over fossil fuels and no fuel is used to generate the power. Since,
no fuel is require so costs for purchasing, transporting and cleaning up plants
is quite low.

2.Reduce Reliance on Fossil Fuels : Dependence on fossil fuels decreases with the increase in the use of
geothermal energy. With the sky-rocketing prices of oil, many countries are
pushing companies to adopt these clean sources of energy. Burning of fossil
fuels releases greenhouse gases which are responsible for global warming.

3.No Pollution : This is one of the main advantage of using geothermal energy since it
does not create any pollution and help in creating clean environment. Being the
renewable source of energy, geothermal energy has helped in reducing global
warming and pollution. Moreover, Geothermal systems does not create any
pollution as it releases some gases from deep within the earth which are not
very harmful to the environment.

Disadvantages Of
Geothermal Energy

Energy
created from geothermal power is safe, clean, simple, reliable and environment
friendly as it is extracted from deep within the earths surface. But despite
these advantages, geothermal energy is not being used widely. Geothermal energy
suffers from its disadvantages as described below.

1.Not Widespread
Source of Energy
: Since this type of energy is not widely used therefore the unavailability of
equipment, staff, infrastructure, training pose hindrance to the installation
of geothermal plants across the globe. Not enough skilled manpower and
availability of suitable build location pose serious problem in adopting
geothermal energy globally.

2.High Installation
Costs
: To get geothermal energy, requires installation of power plants, to get steam
from deep within the earth and this require huge one time investment and
require to hire a certified installer and skilled staff needs to be recruited
and relocated to plant location. Moreover, electricity towers, stations need to
set up to move the power from geothermal plant to consumer.

3.Can Run Out Of Steam : Geothermal sites
can run out of steam over a period of time due to drop in temperature or if too
much water is injected to cool the rocks and this may result huge loss for the
companies which have invested heavily in these plants. Due to this factor,
companies have to do extensive initial research before setting up the plant.

4.Suited To Particular
Region
: It is only suitable for regions which have hot rocks below the earth and can
produce steam over a long period of time. For this great research is required
which is done by the companies before setting up the plant and this initial
cost runs up the bill in setting up the geothermal power plant. Some of these
regions are near hilly areas or high up in mountains.

5.May Release Harmful
Gases
: Geothermal sites may contain some poisonous gases and they can escape deep
within the earth, through the holes drilled by the constructors. The geothermal
plant must therefore be capable enough to contain these harmful and toxic
gases.

6.Transportation : Geothermal Energy cannot be easily
transported. Once the tapped energy is extracted, it can be only used in the
surrounding areas. Other sources of energy like wood, coal or oil can be
transported to residential areas but this is not a case with geothermal energy.
Also, there is a fear of toxic substances getting released into the atmosphere.

I would like to note that I do not share Michael's idea to some extent. I believe that geothermal energy is not as safe and clean as he cited. I found from some articles I have read about this topic that geothermal energy carries risks for evvironment. Hot water from geothermal sources contains hazardous materials such as arsenic, mercury and boron. If these elements realese, it will be very harmful.We can deduce here that it contaminates water as well. In adddition, this energy has an indirect role to play in global warming since it uses machinery like pumps and compressors ,which consume pollutant energy sources, to be produced. It also uses a large volume of water which can be reused fortunately. The most significant concern about this enery is that it can result in seismic activity because of fracturing. however, this renewable source of energy is needed since its advantages overwights its disadvantages and it is still much more environmentally cleaner and safer compared to oil an coal.As a result, by managing the risk associated to it, we can easily meet the future energy demand.

Geothermal energy reminds us of old steam engines. The energy through a boiler tank will build up the pressure which through mechanical meanswill provide us other source of energies.

In order to avoid damaging the ecosystem, and to achieve maximum benefit from this natural source of energy, costs are affected in order to avoid damaging the ecosystem. While Electricity converted through Geothermal steam or hot water, there will be some waste products. Different types of extraction methods will produce environmental damage.

After extracting heat through " Closed Loop " system, most extracted gas and fluids from the well will be fed back by re-injection to the earth. Therefore there will be no loss. However in an " Open Loop " System , large amount of chemicals are released which can be hazardous .

" Scrubbers " a mean to reduce air emissions, can also produce other wastes. Which through costly drying process it should be transferred to waste sites.

The waste free closed loop system is the safer method, which care should be taken to make the injection below fresh water level under the ground. By means of which any contamination is avoided.

Geothermal energy is created by the heat of the earth. It generates reliable power and emits almost no greenhouse gases.
When groundwater seeps below the earth's surface near a dormant volcano, the water is heated by reservoirs of molten rock, usually
at depths of up to 3,000 meters. Wells are drilled to recover the water and once captured, steam and hot water are separated.
The steam is cleaned and sent to the power plant while the water is returned to the reservoir where it helps to regenerate the steam
source.

In addition to providing clean, renewable power, geothermal has significant environmental advantages. Geothermal emissions contain few
chemical pollutants and little waste-they consist mostly of water, which is reinjected into the ground.

Geothermal energy is a reliable source of power that can reduce the need for imported fuels for power generation. It is also renewable
because it is based on a practically limitless resource-natural heat within the earth.

also direct-use applications include heating buildings, growing plants in greenhouses, drying crops, heating water farms and several
industrial processes.

Geothermal energy is a renewable source of energy and it is also
sustainable. It is renewable because the heat is extracted from the earth and
the amount of heat extracted is small compared the huge heat content of the
earth which is about 1031 joules (3x1015 TWh). This heat
is self-replenished by nature. It is also said to be sustainable because the
use of geothermal heat energy by present generation will in no way have a
negative effect on the ability of future generations to also use this form of
energy.

As to whether it is clean, safe and environmentally friendly
is another issue. The energy generated from the Geothermal plant is itself clean,
safe and environmental friendly but the hot fluids from the ground results in
the emissions of CO2, H2S, CH4 and NH3
which also contributes to global warming. Geothermal plants are also known to
cause land instability in certain parts of the world which could lead to earth
quakes.

Compared to conventional sources of energy, geothermal
energy’s emissions and environmental damages are very minimal and hence can
still be considered as a renewable source of energy.

Geothermal energy is relatively clean and environmentally -at least planet earth’s atmosphere would benefit
significantly if geothermal energy would replace half of our total fossil fuel use-.
Also in terms of it availability, geothermal energy can be said to be sustainable
if properly managed/harnessed.

BUT!!!

How safe is it?

On 12th December 2009, AltaRock
an energy company working with the United States energy department to develop
geothermal energy in USA discontinued its exploration at Geysers California. This
came one day after the Swiss government officials permanently shut down a geothermal
plant in Basel because of earthquakes attributed to it in 2006 and 2007. This
trend of geothermal plant shut down due to threat of earthquake is also observed
in other parts of the world with geothermal resources as in Australia and
Germany.

In Landua Germany,
government officials are reviewing the safety of a geothermal energy
project that scientists say set off an earthquake in mid-August 2009, shaking
buildings and frightening many residents of the small city. Like
other earthquakes that have been attributed to geothermal plants, the Landau
temblor was sudden and brief and was accompanied by a sound that in some cases
has been likened to a sonic boom.

Therefore,
notwithstanding the fact that these events have been small and no fatalities
have been recorded, it is very imperative to determine the extent of damage
that geothermal energy can cause and weight those against it benefits.

I like to add some Disadvantages of Geothermal Energy1) Environmental issues - there is a plenty of greenhouse gases under the earth surface which will move to the earth surface and cause the global warming. There are also traces of heavy metals such as mercury, arsenic and boron.

2) Surface instability- Construction of geothermal plants can affect the stability of the land for an example, in both Germany and New Zealand, buildings of geothermal plants lead to subsidence (motion of the Earth surface). There is a possibility if earthquakes due to hydraulic fracturing, which is an important aspect of constructing EGS (ENHANCED GEOTHERMAL SYSTEM) power plants. Examples is the at January 1997, the construction of geothermal power plant in Switzerland triggered an earthquake with a magnitude of 3.4 on the Richter scale.

I would like to add my opinion in this topic.
I believe that like every other source of energy if it is managed properly, geothermal power is a safe and sustainable form of renewable energy. Yes it is renewable energy but this is off topic at the moment.

Non-condensable gases are associated with the operation of geothermal plants like CO2, CH4, S02 and H2S. These gases are indeed dangerous both for humans and the environment.
Modern geothermal stations are now obliged to reinject the water, after they have extracted its energy, back to the well.
This way all the dangerous gasses, minerals and silica are not released to the atmosphere. Also chemicals are responsible for trapping and destroying H2S.

The argument about the Geysers is pretty old now since according to Boyle: “... the level of atmospheric H2S over the Geysers field is now lower than emmited naturally from hot springs and geysers before geothermal development began”.

New technologies made the geothermal energy safe and clean, but because of the early adopted bad reputation development was reduced.

Geothermal Energy is the energy from the head under the earth crust. Resource of this energy is come from the shallow ground to hot water, hot rock (a few mile under the earth surface), and from the very high temperature of magma. So, such energy has been trapped under the earth crust. The way for delivery it is drilling. Although, this kind of energy resource is seen to be an environmental friendly and clean, it is still have some hidden risks. First of all, drilling earth surface for producing geothermal energy might create earthquakes. Moreover, the emission of some hazardous gases (such as hydrogen sulphide) is another side effect from geothermal energy. Such gases are coming to the earth surface along with the hot water.
To sum up, Geothermal Energy is not absolutely or not 100 percent clean and environmentally friendly. It has some hidden risks. For mitigate and prevent those hidden risk, it has to be produced in the correct and cautious way ( concerning about the hidden risks that might occur). If it is produced in the correct way, this energy resource will become to a very good source of renewable energy.

Utilizing the natural resources of the
Earth, geothermal energy has become one kind of popular renewable energy in the
world. Although geothermal energy is a relatively clean, safe, environmentally
friendly and sustainable energy source compared to conventional energy, several
issues about safety and environment should be addressed here:

1. Dangerous
Location Restrict

As we know, the utilization of geothermal energy
has restrict of location, especially around the edge of the tectonic
plates where there volcanic and earthquake are more likely to appear.
There is potential danger if we keep invest huge amount of money on the
geothermal energy infrastructure in these districts. [1]

2．Impact on Environment

Although the risk of emission of a mixture
of gases, notably carbon dioxide (CO2), hydrogen sulfide (H2S),
methane (CH4) and ammonia (NH3) is well controlled in the
modern geothermal electricity plant, we still faced the risk of environment
pollution caused by toxic elements such as mercury, arsenic, boron, and
antimony contained in the hot water in the deep earth. [2]

At the same time, because we may use more water
than the water reinjected to the formation, and finally may cause land
subsidence, it must be noted earlier.

3.
Heat Pollution

Geothermal steam temperature and pressure
is lower than the traditional fossil fuel plant and only has an efficiency of
20%, which causes more cooling water, and may bring more serious thermal
pollution.

As we all know, the earth is divided into 3 parts. The earthcrust, mantle and centrosphere. Normally, the thickness of crust part is totally different ,it varies from several kilometres to 70km. However, when drilling from the surface to the maximum we can, the average temperature increases 3 degrees during 100m. For example, there is a well in Central part of China, the tempareture was 46.7° when people drilled it; somewhere else has a well which its temperature was 180° when it was drilled to 5km. It can be seen that the heat from the earth is incredible!

According to the reserach, the total amount of geothermal energy is around 450,000 times than the whole amount of energy consumption worldwide. What's more, the total energy from geothermal is 170million times than that of all the coal in the world.

However, there are several disadvantages in safe purpose which needed to be concerned:

The efficient geothermal plant is located near the high-risk earthquake parts

Not everwhere has the ability to build it so that it is waste of money if the pruduction is not satisfied

At present, enhanced geothermal systems are widely used for electricity generation in more than seventy countries all over the world. The principle is to fracture rocks by deep prospecting and then inject water into the artificial connected crack belt, which could produce steam for electricity generation for water will be heated by getting in touch with rocks. This concept stems from natural hot water circulation system. Recently, there exists analysis shown that enhanced geothermal systems may lead to earthquake and underground water contamination. When hot rocks are broken by drilling holes, on account of sudden pressure drop, the water inside crack will be vaporized rapidly to steam and further to drive turbine to generate electricity. Drilling itself doesn’t result in earthquake but discharge of steam and waste reinjection may be associated with unstable state of crack belt which could cause earthquake.

As we all know, geothermal energy which is generated by the heat of the earth is basically a relaible source of energy and generates liitle or no greenhouse gases.

One method of generating geothermal energy is by drilling wells into geothermal reservoir where hot water rises and emerges at the surface as steam. The steam is used to drive turbines which produces electricity. In cases where the water is not hot enough to produce steam, it can still be used to heat homes/businesses thereby saving gas/electricity.

It is a very rare source of energy as very few places around the world provide the conditions required to generate geothermal energy. Geothermal reservoirs are located along major plate boundaries where earthquakes and volcanoes are concentrated.

PROS

it is environmentally friendly and creates no pollution

constant power supply is expected unlike wind and solar energy which is subject to weather flunctuations and climate change

Green house gases can be reduced if geothermal and other renewable energy sources are utilized

Electricity is generated from the steam and also hot water can provide heat to homes and businesses

CONS

High installation cost of power plants

Suited to particular region- only regions (hot spots) with hot rocks below the earth can produce steam over a long period of time.

Geothermal energy cannot be easily transported. Once the energy is produced, it can only be used in surrounding areas.

Energy in the form of heat in the earth is very abundant. It is estimated that there is about 10 trillion EJ of Energy produced and stored in the earth. [1]This energy is produced bynaturally occurring radioisotopes in the earth's Core. Geothermal resources are tapped from the energy contained in the earth. There are many technologies that have now been developed to tape these resources in an efficient way. Some of these are the flash steam system, the dry steam system, the binary cycle system and the single bore geothermal extraction system. A number of them have been enhanced so that they have minimal effect on the environment and provide energy efficiently.

Though geothermal energy is abundant, it requires a lot of capital to set up a geothermal plant and not all sites are suitable for geothermal energy extraction. Despite this, for places
where the energy could be extracted from the earth using available technologies great gains could be made because geothermal energy as a renewable resource is very sustainable. This is due to the fact that the energy source coming from the earth can never be depleted and its self sustaining.

With the advantage of sustainability of geothermal energy source in mind, the United States of America and the United Kingdom are making effort to build more geothermal plants. It must be however noted that not all locations can produce geothermal energy in
economically sustainable way.

Geothermal energy is a renewable source that becomes economically more attractive as the cost of conventional energy increases.

The source of geothermal energy is from the earth crust. The known geothermal ‘hot spots' therefore it is a sustainable energy source because have been associated with the hot plate tectonic processes.

The energy produced from this technology is environmentally friendly since the steam used for turning the geothermal turbine is generated along side with water and the water is re-injected into the wellbore. This is certainly a continuous process one that could be considered safe and clean.

The safety issues with this technology varies, first the known geothermal regions are linked with hot molten magma boiling beneath the earth crust. They are capable of delivering a combination of water and steam at temperature up to 300oC, the concern with this technology is that; if the molten magma in the source rock gets to the surface. The consequences would be Its ability to burn any
living thing within its reach to death [1]. Secondly, the risk associated to this technology is that its operating site could be susceptible to earthquake. As
seen in Europe. Having analized the Pros and Cons attributed to this technology literally, as much as our hearts are in it we also have to recognize the importance of low carbon footprint.

With current industrial scale showing that this technology contributes a great deal to the world's energy supply with less carbon footprint. My stand is on the use of geothermal technology in a safe and efficient ways to generate energy.

As my colleagues have mentioned above, Geothermal energy is
one of the cleanest energy source usedto produce electricity. As we as well know that there is nothing that
is completely safe. The only advantage that geothermal energy has is that it
does not pollute the environment unlike coal and other energy sources thereby
helps to clean the environment thereby helping to reduce global warming and
pollution since it doesn’t release gases which are harmful to the environment but
sometimes geothermal sites may contain some poisonous gases that can escape
deep within the earth, through the holes when drilled during construction.

Geothermal energy also has an environmental impact from site
evaluation, construction, operation, and decommissioning of geothermal energy
facilities. All this have potential impact on the health, environment and
safety either direct or indirect. Mitigation measures needs to be applied to
reduce the impacts from geothermal energy .In order to identify and implement
appropriate mitigation measures, the potential impacts of it must first be
assessed. The following measures needs to be in n place to mitigate the impact:
conducting a proper safety assessment to describe potential safety issues be
avoided or mitigated, the actions to be taken and how effective the mitigation
measure will be, and the cost-effectiveness of the measure. Also proper land
use is also essential by providing adequate public notice of any planned
activities.

I agree with many of the opinions above, that in the large scale there is environmental hazards associated with geothermal power. However, at the smaller domestic scale, it can be much safer and more efficient. Not all areas have the potential to harness geothermal heat but most areas can produce a small amount for domestic needs. Many building companies are now able to incorporate geothermal heat systems into new building foundations, which means there is a much reduced footprint on the surrounding area. The efficiency of a geothermal device in a domestic property means that you can use ~3time less conventional energy to produce the equivalent heat in traditional designs.

At last; a colleague who has identified geothermal for domestic use, this is where geothermal is king, due to a natural global phenomenon in which around two meters below ground the temperature is constant at around ten to sixteen degrees Celsius, it’s possible that with around one hundred meters of three centimeter diameter plastic piping installed at two meters below ground buried in a trench, around three kilowatts of heat energy can be produced. The hundred meters of tubing does not have to be installed as a straight run and may be coiled up and installed as a child’s slinky toy; thereby only requiring around thirty meters of actual trench space. Of course the tubing does not need to be horizontal and a vertical shaft would produce more heat per tube length and further to this of course, there is no limitation on the number of pipe runs!

So here we have an application of geothermal energy that is truly global, may indeed be used for both heating and cooling (in warmer climates the process would be reversed, sucking heat out of a building) is totally environmentally friendly (assuming a Stirling motor is used in place of an electric motor) and would go a long way to solving the world domestic energy needs!

Geothermal energy is a renewable energy, which produce power by digging out the heat stored inside the earth. Geothermal energy is a clean source of energy. Development of this form of energy can reduce the dependency on fossil fuel. Geothermal energy has its own advantages and disadvantages.

Advantages of geothermal energy are: Running cost is very low as it doesn’t use any fuel to generate power. It reduces the dependency on fossil fuels. The main and most important advantage of geothermal energy is it doesn’t create any pollution. It helps to reduce global warming and it doesn’t create any harm to the environment. Any new and cheap source of energy is a boost for the economy. It creates many jobs and reduces the cost of power.Disadvantages of geothermal energy are: Source of energy is not wide spread. The installation cost of geothermal energy is high. It is only suitable for some particular areas. Geothermal energy cannot be easily transported.

Geothermal Energy is really a clean, safe, environmentally friendly and sustainable energy. There are a lot of evidences to prove this argument. For instance, Iceland is located in the north Atlantic Ocean which is the second largest island in European . Special geological structure make the Iceland underground heat rolling and it becomes the world's most abundant geothermal resources of the country. The latest geothermal resources research find that: Iceland crustal thickness is from 0 to 10km range can provide the geothermal resources content for 300 million TWH. The crust thickness from 0 to 3km can provide the scope of the geothermal content 30 million TWH. Technology availability is for 1 million TWH. If all the geothermal energy is used to power generation, it can provide more than 80 billion degrees.85% of the population in Iceland utilize geothermal for heating. In addition, they also build the geothermal power generation station.

However, this source is not so common worldwide. The geographical limitations are the significant restriction for this technology. Not all the countries have the chance to use this renewable energy. That is to say, even though it is clean and environmental, it cannot replace the oil and gas and take a large proportion in the future energy matrix.

This is a form of energy that is harnessed from the heat of the earth. There are three major elements required to generate geothermal energy namely: a reservoir, fluid (steam or hot water) and a source of heat. Of all three elements, the heat source must be natural and the other elements can be artificial. Geothermal energy is a renewable form of energy because water is regenerated in its water cycle, has a low carbon footprint and it is also a sustainable form of energy because it can be harnessed without jeopardizing opportunities for future generations [1][2].

Overtime, certain risks involved in the production of geothermal energy has been assessed and preventive barriers have been put in place [3][4][5].

Risk Mitigation
Noise pollution Minimised when plant becomes operational.
Land subsidence Re-inject used geothermal fluid to the reservoir.
Well blowout Install a blow out preventer during drilling.
Chemical or Thermal pollution Re-inject used geothermal fluid to the reservoir
Solid waste disposal Proper disposal of drill cutting after drilling

Geothermal energy has a great potential in the energy mix, it is one of the forms of renewable energy that provides a strong base load power. Its application is either direct or indirect.

Geothermal energy, a renewable
energy source, can be defined as heat from the Earth. Unlike other renewable
sources of energy, which are dependent on weather fluctuations and climatic
changes, the resources are available 24 hours a day, 7 days a week, due to the
indefinite availability of the Earth's heat.

Emissions: Unlike fossil fuel plants, geothermal
power plants do not burn fuel, and hence release no air emissions. Plumes seen
rising from geothermal powered plants are vapor emissions, and not smoke. With
regards to hydrogen sulfide, it is now routinely abated at geothermal powered
plants, resulting in the conversion of over 99.9 percent of the hydrogen
sulfide from geothermal non-condensable gases into elemental sulfur, which can
then be used as a non-hazardous soil amendment and fertilizer feedstock [1].

Noise Pollution: The "noise" emitted from
geothermal plants, is said to be less or equivalent to rustling of leaves from
breeze, and thus is not an issue of concern

Water Use: The average freshwater use per day of
geothermal plants is estimated to be at about 5 gallons per megawatt hour,
while natural gas averages at about 361 gallons per megawatt hour.

Water Quality: In order to prevent the
cross-contamination of brines with groundwater, the geothermal fluids are
injected back into the geothermal reservoirs. This injection helps in the
reduction of surface water pollution and in turn would increase the geothermal
reservoir resilience

Wildlife and Vegetation: Geothermal plants are
designed to minimize the potential effect upon wildlife and vegetation, prior
to an environmental review carried out before commencement of construction, and
they are constructed in accordance with a host of state and federal regulations
that protect areas site for development [1].

Geothermal energy is the lava temperature
power from the interior of the earth. It is not only non-polluting and clean
energy, but also it is the renewable energy if the heat extraction rate does
not exceed the speed of supplement. Geothermal energy is now a widely used new
energy. We can take advantage of geothermal energy to generate power, heating,
farming and medical practice to bring benefit to the human. Different from the
instability of the solar and wind energy, geothermal energy is not only
reliable and rich, but also it will not have the greenhouse gases emission,
that will not harmful for the earth environment.

In conclusion, geothermal energy is likely
to become an important part of the future energy mix.

Geothermal energy is a clean and reliable source of energy. Geothermal energy is the thermal energy generated and stored in the earth. Usually as you go deep into the earth surface, the temperature increases according to the geothermal gradient of the location. This energy can be harnessed in various ways to be used in generating electricity. There are different methods available in which geothermal energy has been harnessed. It is a clean and environmental energy source because it does not pollute the environment or cause damage to the environment.
There are three main technologies used to harness geothermal energy. They include generation of electricity from the earth’s heat. The heat energy from the earth is used to boil water and produce steam which is then used to run power generators thereby producing electricity. Also there exist technology to produce heat directly from the water within the earth and the heat from the ground is used to heat and cool buildings.

Geothermal energy still has some safety issues associated with it. Some are
(1)There is the risk of methane and CO2 emission together with unwanted gases. These gases can be emitted as we move down into the earth surface
(2)There could be damage to the earth crust as a result of drilling into it.

There are several methods for applying geothermal energy. I would like to note that although this type of energy application is considered as a green energy, it has some safety issues which may be increased or decreased based on what method of exploitation we are using.

In some methods such as dry steam power plants and flash steam water plants, a lot of fractures should be done in the wells which cause some changes in the nature of the earth around the wells. Also, some greenhouse gases such as H2S are produced during geothermal energy application. Moreover, the hydrothermal fluids which are used in these methods results in polluting the underground water.

From my point of view, Dual Pipe Heat Exchanger technology which is used in Oil and Gas abandoned wells are completely in line with green energy target. The only disadvantage that I can mention is that the fluids which are used in this method are volatile and toxic.

According to Downing, R.A., et al, the earth's natural heat
is derived primarily from decay of long-lived radioactive isotopes. There are
hot and thick rock bodies surrounding the nuclear degeneration process with
fluid transporters around them. Due to the presence of these rocks and fluids,
there are no effusive hazardous wastes.

It is this heat that is generated within the earth that is
harnessed due to heat transmission from rock bodies to the other. Di Pippo (1984)
writes that when temperatures of underground water exceed 200 degrees Celsius,
they are used for electricity generation. Other models have been
developed to generate electricity at temperatures below the
propounded value.

The main types of geothermal energy generation cycles
include single borehole system, flash steam, binary cycle and dry steam cycle.

Barbier, E., postulates on p 37 of his book Renewable and
Sustainable Energy Reviews 6 (2002) that there is a very low possibility of
volcanic eruptions in the harness of this form of energy. Other forms of risk exposed
by geothermal energy generation include water pollution, land subsidence (areas
of low rock strength) and induced seismicity.

The discharged fluids may also pose a hazard to the aquatic
environment should the discharged fluids from its procedure be ill-disposed of,
Barbier continues. Also, the water table can be polluted in the process of
drilling and when the single borehole cycle is used.

It is imperative then that, certain studies and mitigations
should be proposed for the various types of geothermal power generation employed.

References

Enrico Barbier, Geothermal energy technology and current status:
an overview

Downing and Gray, pg 1, Nature of Geothermal Energy,
Geothermal Energy: The Potential in the UK

While there are many environmental impacts involved in the production of geothermal energy such as air, water and noise pollution, I believe one of the major risks to consider is that of earthquakes.

The hydraulic fracturing process used in geothermal energy has been found to induce seismic activity. This brings about the issue of liability, an earthquake is rarely considered to be anything but an act of god (natural, not supernatural). Therefore if humans are now also responsible for putting the world at risk, there must be a method of monitoring and logging it. In order to assign blame for any damages or injuries down the line.

There is a counter argument that states that the highest levels that have been created artificially are only 2.3 on the Richter scale, hardly an extreme level. However who is to say that this maximum will not increase as techniques develop, is it really worth the risk?

There is no doubt that geothermal energy is the best example of environmentally sound source of energy. Being clean of this type of energy is highlighted by 200 lbs/Mw-h carbon dioxide emission (Green, 2012). Statistics illustrate that this is about 13% of CO2 emission through oil and gas production (Green, 2012).
How about sustainability? Will it be viable in the not too distant future?
It would be more interesting that the cost of geothermal has become 1/3 during 3 decades ago. This is happened by reducing the expenditure in each phase of exploration, drilling, exploitation and production. For instance, there has been significant progress in understanding the characteristics of formation and rock type by state of the art seismic method. There has been also the discovery which marks a significant technological advance by utilizing simhole drilling. This cost of drilling has been almost halved owing to this approach (Kutscher, 2000).
Put it into a nutshell, taking into consideration of disadvantages ( e.g. rarely approachable depends on appropriate depth), I would like to say that there is no necessity for accessing each type of energy around the world. What about the Importing and exporting the energy throughout the world? Anyhow, I cite that geothermal as a clean and sustainable energy might be a superior source of alternative in the not too distant future.

Geothermal energy is the capture of heat from deep under the ground,
usually by pumping water down, and then turning that heat into
electricity. The same water can be used over and over.

1. Depletion of Resources

The process of extracting geothermal fluids (which include
gases, steam and water) for power generation typically
removes heat from natural reservoirs at over 10 times their
rate of replenishment. This imbalance may be partially
improved by injecting waste fluids back into the geothermal
system.

2. Damage to geothermal features

Natural features such as hot springs, mud pools, sinter
terraces, geysers, fumaroles (steam vents) and steaming
ground can be easily, and irreparably, damaged by geothermal
development. When the Wairākei geothermal field was tapped
for power generation in 1958, the withdrawal of hot fluids
from the underground reservoir began to cause long-term
changes to the famous Geyser Valley, the nearby Waiora
Valley, and the mighty Karapiti blowhole. The ground sagged 3
metres in some places, and hot springs and geysers began to
decline and die as the supply of steaming water from below
was depleted.

3. Subsidence

Extracting geothermal fluids can reduce the pressure in
underground reservoirs and cause the land to sink. The
largest subsidence on record is at Wairākei, where the centre
of the subsidence bowl is sinking at a rate of almost half a
metre every year. In 2005 the ground was 14 metres lower than
it was before the power station was built. As the ground
sinks it also moves sideways and tilts towards the centre.
This puts a strain on bores and pipelines, may damage
buildings and roads, and can alter surface drainage
patterns.

4. Polluting waterways

Geothermal fluids contain elevated levels of arsenic,
mercury, lithium and boron because of the underground contact
between hot fluids and rocks. If waste is released into
rivers or lakes instead of being injected into the geothermal
field, these pollutants can damage aquatic life and make the
water unsafe for drinking or irrigation.

A serious environmental effect of the geothermal industry
is arsenic pollution. Levels of arsenic in the Waikato River
almost always exceed the World Health Organisation standard
for drinking water of 0.01 parts per million. Most of the
arsenic comes from geothermal waste water discharged from the
Wairākei power station. Natural features such as hot springs
are also a source of arsenic, but it tends to be removed from
the water as colourful mineral precipitates like bright red
realgar and yellowy green orpiment.

5. Air Emission

Geothermal fluids contain dissolved gases which are
released into the atmosphere. The main toxic gases are carbon
dioxide (CO2) and hydrogen sulfide
(H2S). Both are denser than air and can collect in
pits, depressions or confined spaces. These gases are a
recognised hazard for people working at geothermal stations
or bore fields, and can also be a problem in urban areas. In
Rotorua a number of deaths have been attributed to hydrogen
sulfide poisoning, often in motel rooms or hot-pool
enclosures. Carbon dioxide is also a greenhouse gas,
contributing to potential climate change. However, geothermal
extraction releases far fewer greenhouse gases per unit of
electricity generated than burning fossil fuels such as coal
or gas to produce electricity.

Geothermal energy is unarguably one of the cleanest sources of renewable energy since the power plants utilizing this energy don't burn fossil fuels for electricity, the emissions they produce remain very low; as much as 97% less than a fossil fuel plant. The advantages of geothermal energy range from environmentally friendly, renewable, sustainable, stable and full of potential. However, as pointed out by many, there are certain disadvantages of geothermal energy that cannot be ignored. There are environmental issues relating to the drilling and construction of geothermal energy plants such as the release of greenhouse gases from below the earth's surface and earthquakes due to hydraulic fracturing as in the case of the 1997 earthquake in Switzerland at a geothermal construction site.
However, when compared to other sources of energy such as fossil fuels the disadvantages of geothermal energy are negligible. Yes, it is an expensive source of energy with the cost of a 1 MW capacity plant running into $2-7 million but it is an industry with potential, hopefully with regulations and further research geared at reducing the risks involved and finding cost effective ways, it remains one of the renewable energy sources that can be explored and developed.

Geothermal energy is an eco friendly source because you arejust converting the heat energy without leaving behind any residue. During conversionthere is no emission of polluting gases such as carbonmonoxide as in case ofpetroleum oil.

Yes, but it's not usually 100% Eco-Friendly, unless you alsohave solar or wind-power.

There's a pumping system that sends liquid through underground pipes, then anelectrically driven compressor and a heat exchanger concentrate the Earth'senergy and release it inside the home at a higher temperature. Ductworkdistributes the heat to different rooms via furnace with blower. The pump,compressor, heat exchanger, and furnace blower all use electricity.

Other than the electricity used there's no emissions (because nothings burned),no waste, no mining, no transportation of materials that might spill.

This electricity might be coming from a coal powered plant - thus not entirelygreen. But if it's coming from solar or wind, then it's 100% eco-friendly. Buteven if the electricity is coming from a non-greensource, the amount ofelectricity needed to run a geothermal system is minor - estimated at $300 to $400per year for both heating and cooling.

Geothermal energy is considered to be clean and reliable source of a renewable energy when comparing to other sources such as conventional fossil fuels. However, there are safety issues with this source of energy, firstly in addition to dissolved gases, heated water from geothermal source can hold up dangerous chemicals such as arsenic, boron, mercury and antimony in solution trace amounts of toxic elements.As the water cools, these can cause environmental damage if released, but with the modern method of injecting cooled water back into the earth crust to improve production has helped in reducing this environmental risk thereby reducing the risks as low as reasonably practicable (ALARP). Secondly, another concern is during plant construction geothermal can affect land stability hence can trigger earthquake when hydraulically fracturing the earth crust.For example, in Basel, Switzerland a geothermal project was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter scale occurred close to a week of water injection process during the project. This created many concern whether geothermal energy is safe or not. Nevertheless, in other to mitigate this risk a proper site location need to chosen where earthquake is low to avoid this environmental impact and also ensuring proper safety measures through safety legislations [1].References[1]http://en.wikipedia.org/wiki/Geothermal_energy#Environmental_effects